46 BC

By place

Roman Republic

• Consuls: Gaius Julius Caesar, Marcus Aemilius Lepidus.
• Civil War:
• * January 4 – Titus Labienus fights Julius Caesar in the Battle of Ruspina.
• * April 6 – Caesar defeats the combined army of Pompeian followers and Numidians under Metellus Scipio and Juba I of Numidia at Thapsus. After the battle Caesar grants Legio V Alaudae the right to bear the elephant symbol on its shields and standards, for bravery against a charge of elephants.
• * April 20 – Cicero, in Rome, writes to Varro "If our voices are no longer heard in the Senate and in the Forum, let us follow the example of the ancient sages and serve our country through our writings, concentrating on questions of ethics and constitutional law."
• * Caesar's erstwhile mistress, Queen Cleopatra VII of Egypt, and his son by her, Caesarion, take up residence in one of the dictator's estates on the Tiber.
• * September 26 – Julius Caesar dedicates a temple to his mythical ancestor Venus Genetrix in fulfillment of a vow he made at the battle of Pharsalus.
• * November – Caesar leaves for Hispania to deal with a fresh outbreak of resistance.
• * Caesar reforms the Roman calendar to create the Julian calendar. The transitional year is extended to 445 days to synchronize the new calendar and the seasonal cycle. The Julian Calendar would remain the standard in the western world for over 1600 years, until superseded by the Gregorian Calendar in 1582.
• * Caesar appoints his nephew Octavian his heir.
• * Caesar subdues a mutiny of his Tenth Legion.
• * Caesar celebrates his Gallic Triumph, after which Vercingetorix is executed. The celebrations run for forty days in Rome, and include public banquets, plays and gladiatorial games.
• Vitruvius describes Etruscan and Roman architecture.